Figure 3: Dissolution of a surfactant-containing fiber in water. Reproduced from
US Patent Application 200120021026.

rheology modifier and other additives that confer the desired
attributes of the finished article that could eliminate the water from a formulation and printing thereon could radically
reduce the amount of packaging material.

In the Glenn et al. patent application, the surfactants are clas-sified into foaming and non-foaming types. Formulators wouldrecognize the foaming type to be similar to shampoos and cleans-ers, and the non-foaming type to be more like conditioners. Thestructuring polymer is a water-soluble polymer such as poly(vinylalcohol), poly(acrylate), PVP, PEO, starch, pullulan or celluloseethers. The extensional rheology modifiers enable the formationof thin fibers rather than a spray of droplets when the fiber isspun because liquid jets tend to break up into droplets as a resultof Plateau-Rayleigh Instability. For the production of sprays, oneseeks conditions that favor Plateau-Rayleigh instability, but forthe production of fine fibers it is important to try to avoid suchinstability. Plateau-Rayleigh instability results from perturbationsthat are always present in a thin liquid tube. Some of the pertur-bations can grow until they pinch the fiber into drops. The thinnerthe liquid tube, the more likely it is to be unstable. This is usuallydemonstrated by controlling the flow of water from a faucet. Asthe tap is slowly turned down, the liquid stream flowing from thefaucet becomes progressively thinner and eventually breaks intodrops. If a liquid is viscous or it contains an associating solute oran entangled polymer solution, then the liquid can be spun intomuch finer filaments, due to the increase in extensional viscosityof the system. Thus the extensional rheology modifiers are re-quired to enable spinning of extremely fine fibers. This is espe-cially important in this case because the dissolution time in thepalm of the hand will be faster as the dissolvable fibers in theproduct become ever finer. Extensional rheology modifiers areusually high molecular weight soluble polymers. In this case itseems that high molecular weight poly(ethylene oxide) is pre-ferred. Very fine fibers can be made via spunbonding, electrospin-ning, meltblowing or melt fibrillation.